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# AQA A Physics Unit 4 24th Jan 2012

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1. Q. 23
Attached Files
2. circular motion mixed questions.rtf (1.20 MB, 1720 views)
3. does anyone have a mark scheme for the exam style ques from the text book ?
4. also does anyone have the june 2011 paper and mark scheme ?
5. (Original post by mk207)
Q. 23
The answer is D,
cuz if you equate mw^2r to Bqv,
according to the question, q=e and m=m obv,
Using v=wr we can cancel v on both sides.
So, mw=Be
then using w=2pi/t
we get 2pim/T = Be
rearrange that to make T the subject and there you go!
6. Could somebody explain to me the answer to Q2 June2010
http://idisk.me.com/mail.matt/Public...W-QP-JUN10.PDF

I thought i just had to use "ft=mv-mu" but with that i get 100 not 50.
And Q4 as well thanks
Thanks
7. (Original post by handsome7654)
The answer is D,
cuz if you equate mw^2r to Bqv,
according to the question, q=e and m=m obv,
Using v=wr we can cancel v on both sides.
So, mw=Be
then using w=2pi/t
we get 2pim/T = Be
rearrange that to make T the subject and there you go!
that's what i did and i got D but my mark scheme says the answer is B...
8. (Original post by soldiersixteen)
Could somebody explain to me the answer to Q2 June2010
http://idisk.me.com/mail.matt/Public...W-QP-JUN10.PDF

I thought i just had to use "ft=mv-mu" but with that i get 100 not 50.
And Q4 as well thanks
Thanks
You do use the equation Ft = m(v-u)

Ft = Area = (5000*40)/2 = 100,000

100,000 = m(v-u)
100,000 = 2000(v-0)
50 = v

I'm not sure about Q4, sorry.
9. (Original post by schizopear)
that's what i did and i got D but my mark scheme says the answer is B...
I've got that question in a booklet made by my college, and the answer in their mark scheme is D. I agree with handsome7654's working, so it must just be a mistake in the mark scheme.
10. (Original post by jones_wise)
I've got that question in a booklet made by my college, and the answer in their mark scheme is D. I agree with handsome7654's working, so it must just be a mistake in the mark scheme.
i thought (hoped!) it might be a mistake - thanks
11. How do you do this

The diagram shows two charges, +4 μC and –16 μC, 120 mm apart. What is the distance from the +4 μC
charge to the point between the two charges, where the resultant electric potential is zero?
A) 24mm
B) 40mm
C) 80mm
D) 96mm

Thanks
12. (Original post by soldiersixteen)
How do you do this

The diagram shows two charges, +4 μC and –16 μC, 120 mm apart. What is the distance from the +4 μC
charge to the point between the two charges, where the resultant electric potential is zero?
A) 24mm
B) 40mm
C) 80mm
D) 96mm

Thanks
you use the electric potential formula

V=Q/4piepsilon0 x r but the 4piepsilon0 cancels for both so jus ignore it

so for the 4uC you do V=4uC/120 and for the -16uC you do V=-16uC/120-x

equate them and solve for x you should get 24mm
13. (Original post by kimmey)
you use the electric potential formula

V=Q/4piepsilon0 x r but the 4piepsilon0 cancels for both so jus ignore it

so for the 4uC you do V=4uC/120 and for the -16uC you do V=-16uC/120-x

equate them and solve for x you should get 24mm
Thanks.
When i equate them, I get
480u-4ux= -1920u
-4ux=-2400u
x=600

where am i messing up?
14. (Original post by soldiersixteen)
Thanks.
When i equate them, I get
480u-4ux= -1920u
-4ux=-2400u
x=600

where am i messing up?
Do it like this;
Cuz the sum of the potentials at a distance x away from 4uC is 0, you get
+4u/4piepsilon0(x) - 6u/4piepsilon0(20-x) = 0, then add 6u/4piepsilon0(12-x) to both sides,
4u/x = 6u/120-x (the 4piepsilon0 bit cancels), then multiply by (120-x)
480u - 4ux = 16ux
so x = 480u/20u = 24mm!
15. (Original post by mk207)
Q. 23
Hi I got the answer of D, is it possible for you to upload a markscheme for these questions if yuo have one? Thanks
16. (Original post by savage903)
Hi I got the answer of D, is it possible for you to upload a markscheme for these questions if yuo have one? Thanks
there you go
Attached Files
17. circular motion mixed questions ms.rtf (172.2 KB, 106 views)
18. I have just spent all day printing off every multi choice question from the past 10 years. Highligting the right answer and cutting them out. Then placing them in 7 piles (pile for each topic). After removing recent questions and questions that have already been repeated once I think I can guess a few of out questions, well the ones they will be re-using anyway.
19. can you put them up ???
20. (Original post by maths134)
I have just spent all day printing off every multi choice question from the past 10 years. Highligting the right answer and cutting them out. Then placing them in 7 piles (pile for each topic). After removing recent questions and questions that have already been repeated once I think I can guess a few of out questions, well the ones they will be re-using anyway.
could you PM them please to me?
21. (Original post by maths134)
I have just spent all day printing off every multi choice question from the past 10 years. Highligting the right answer and cutting them out. Then placing them in 7 piles (pile for each topic). After removing recent questions and questions that have already been repeated once I think I can guess a few of out questions, well the ones they will be re-using anyway.
Can I ask how you got access to all those past papers? If there is a website for them, can u give me the link plzz?? Really need some practice cuz iv only been getting C/Ds on my practice papers!!
22. If you guys want to spend a day working it out, you welcome to...

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